The present invention relates generally to optical projection lenses, and more particularly, to optical projection lenses for use in projecting three dimensional images.
Movies have been recorded on film in three-dimensional formats for 100 years or more major cinema releases occurred in the 1950's using dual strips and dual projectors and a dual lens side-by side anamorphic formats. In the 1980 era a top-bottom format became popular. The industry standard for this format is SMPTE 257. The ultimate goal for 3D projection has always been to provide the same amount of light to the eye in 3D that is provided with a standard 2D presentation. The present invention resolves this issue. Existing 3D film projection lenses are limited to screen widths of 40 feet. It would be desirable to have a lens that can project images wider than 40 feet.
With the current acceptance of digital 3d presentations as a viable medium for cinema and other venues, and the lower than expected roll out of digital systems to the exhibition community a 3D film solution is appropriate to fill this gap on a world wide basis.
3D film projection lenses utilizing a top/bottom truncated design have always had reliability issues in regards to the failure of polarizers due to heat related issues. U.S. Pat. No. 4,235,503 issued to Condon attempted to resolve this issue by using an ultra violet light filter and mechanical heat sink. A current version has added truncated anti-reflection plates to the input side of the truncated optics with limited success. This has resulted in additional problem in that with this added hardware, the lens back focus and radial clearance dimensions do not allow it to be used on a significant number of projector types and models.
The two lens sets are converged using adjustments at the rear of the lens in a vertical movement. When installed into a projector this is a difficult task and requires removal and reinstallation to optimize. There is a small adjustment range for setting the back focus of both lens sets, but not sufficient to handle significant keystone issues in theatres with balconies.
A projector aperture plate is cut for the film format height. If the aperture plate is not cut perfect, or the projector moves, spill will occur and the window port of the booth will have to be masked by hand.
There is no known split-lens 3D projection lens design that uses wire grid polarizers that can withstand the heat produced by high-power projectors. There is no known split-lens 3D projection lens design that provides for rotational convergence of the image projected by the lens. There is no known split-lens 3D projection lens design that optionally employs a hot mirror located after the lenses to help reduce heat on polarizers. There is no known split-lens 3D projection lens design that provides for independent focus adjustment of the right eye image with sufficient range to compensate for keystone issues. There is no known split-lens 3D projection lens design that integrates an adjustable aperture plate into the lens to resolve light spillover that typically occurs above and below the image on the screen and which requires a projectionist to manually mask the port window of the projection booth.
It would be desirable to have an improved optical projection lens for use in projecting three-dimensional images. It would also be desirable to have an optical projection lens that overcomes the limitations of projection lenses that use conventional film polarizer material. It would also be desirable to have an optical projection lens that allows for rotational convergence of the projected image. It would also be desirable to have an optical projection lens that optionally employs a hot mirror located after the lenses to help reduce heat on polarizers. It would also be desirable to have an optical projection lens that employs a quarter wave plate for use in projecting circularly polarized light images. It would also be desirable to have an optical projection lens that provides for independent focus adjustment of the right eye image to compensate for keystone problems. It would also be desirable to have an optical projection lens that integrates an aperture plate into the lens to resolve light spillover that typically occurs above and below the image on the screen.